Preparation, Microstructure and Mechanical Properties of In-Situ TiC/Al-Si-Fe Aluminum Matrix Composites

In-situ TiC/Al-Si-Fe aluminum matrix composites were prepared by stirring casting method with the addition of titanium agent and carbon powder (the contents of Ti and C elements X = 0, 0.40, 0.60, 1.00wt.%) in Al-12%Si-1%Fe alloys. The microstructure and mechanical properties of aluminum matrix composites were studied by OM, SEM/EDS, XRD and tensile test. The strengthening mechanism and the reasons for the poor increase in yield strength were discussed. The spontaneity of TiC formation in chemical reaction thermodynamics was confirmed. The results showed that when Ti and C were added, TiC particles were formed by in-situ reaction, provided the core for heterogeneous nucleation of alpha-Al8Fe2Si, the beta-Al5FeSi was modified to alpha-Al8Fe2Si. The transformation of beta-Al5FeSi to alpha-Al8Fe2Si produced Si, so that the yield strength did not greatly improve. For all that, the ultimate tensile strength and elongation of the experimental materials have been greatly improved. With the increase of Ti and C contents, TiC particles made the aggregated Chinese-script-shaped second beta-Al5FeSi phases deteriorate, disperse, and uniformly exist in the matrix, and the dispersed second phases mainly contained alpha-Al8Fe2Si phase. When X = 1.00wt. %, due to the heterogeneous nucleation and modification of TiC, the second phases were uniformly distributed, which made the matrix alloy obtain the best mechanical properties.